1. Field of the Invention
The present invention relates to a wiper blade member for an ink discharge face of an ink jet recording head, an ink jet recording apparatus equipped with such wiper blade member, and an ink jet recording method.
2. Related Background Art
In an ink jet recording head, it is required to always clean an ink discharge face, thereby maintaining a stable discharge state. For such cleaning, various proposals have been made.
Regarding a wiper blade member, Japanese Patent Application Laid-open No. H09-076517 proposes to select a rubber hardness of a wiper blade within an optimum range, thereby achieving an improvement in the cleaning performance.
Also Japanese Patent Application Laid-open No. H05-201014 discloses an ether type polyurethane rubber as an optimum material for the wiper blade. It also discloses providing the ether type polyurethane rubber with a water repellent property to suppress an ink extraction from an ink discharge port, thereby improving the wiping performance.
In the recent ink jet recording, pigments are increasingly employed as a colorant of an ink, particularly a black ink, to be used. Such use of pigment is to achieve a high color development density and to improve a water resistance of a print.
In case of employing a pigment-based ink, a prior wiper blade may induce a deterioration in the print quality in a long-term use.
The wiper blade disclosed in Japanese Patent Application Laid-open No. H05-201014 has an excellent performance, but a further improvement is desirable for the use of a pigment-based ink. Japanese Patent Application Laid-open No. H05-201014 deals with an abrasion resistance of the wiper blade and a water repellency to the ink. The water repellency of the wiper blade to the ink is improved by adding a water repellent material to a polyurethane prepolymer constituting the wiper blade.
However, such method may be difficult, in case of employing a pigment-based ink as a recording ink, to maintain a high water repellency. In general, a pigment-based ink employed in ink jet recording utilizes a dispersion with a central particle size of about 50-150 nm, but such ink also contains a large number of particles of a size of about 20 nm or less, and such small particles are estimated to stick to the wiper blade surface, thereby inducing a deterioration in the water repellency. Causes of such phenomenon are estimated as follows.
In the aforementioned wiper blade, an addition amount of the water repellent material is limited, and the polyurethane and the water repellent material are present in mixed manner on the wiper blade surface. As the urethane compound contains a basically hydrophilic urethane bond, the pigment particles of above-mentioned small size stick to such hydrophilic portion.
Also at the formation of the wiper blade, surface irregularities of an order of nanometers are formed and the pigment particles of small size stick to such surface irregularities. In an example of Japanese Patent Application Laid-open No. H05-201014, a surface of a formed wiper blade showing presence of a water repellent material, in an observation under a microscope, is defined as “particles” while a surface not showing such particles is defined as “mutually dissolved”, but the irregularities in the nanometer order are assumed to be present even in those described as “mutually dissolved”.